Process for conversion of hydrocarbons on a catalyst with controlled acidity

ABSTRACT

The invention relates to a process for conversion of hydrocarbons in the presence of at least one catalyst with controlled acidity, characterized in that the level of activity of said catalyst in isomerization of the cyclohexane is less than 0.10 and/or in that the ratio of toluene hydrogenation activity to the cyclohexane isomerization activity is greater than 10.

[0001] It is known that the catalysts for conversion of hydrocarbons andin particular for hydrotreatment of residues are deactivated by metaldeposits, such as vanadium sulfide and nickel sulfide, and by cokedeposit. Coke deposit is known for being increased when the acidity ofthe catalyst increases.

[0002] The applicant discovered, surprisingly enough, that the use ofcatalysts of controlled acidity and/or the monitoring of theconcatenation of the catalysts to use the most acidic catalyst secondleads to quite better performance levels. The invention thereforerelates to a process for hydrocarbon conversion, for example,hydrotreatment, and more particularly hydrodesulfurization of residuesthat were previously partially demetallized consisting in moving apartially demetallized residue onto at least one catalyst of controlledacidity.

[0003] These catalysts are characterized in that their acidity islimited and/or that the ratio between their performance level in ahydrogenation reaction is to a large extent greater than theirperformance level in an acidity test reaction. In the case where twocatalysts that have controlled, but different acidity are used in one ormore reactors, it is recommended to concatenate them in the followingway:

[0004] if a single one of the two catalysts contains cobalt, it ispreferable to position the latter upstream from the second catalyst thatdoes not contain cobalt,

[0005] if both or neither of the two contain cobalt, it is preferable touse as a second the more acidic catalyst or the catalyst with thesmallest hydrogenation/acidity ratio.

[0006] The acidity and the performance level of hydrogenation areevaluated by a catalytic test of a mixture of model molecules: thehydrogenation of toluene and the isomerization of cyclohexane. Accordingto this test that is described below and under these measuringconditions, the level of activity in isomerization of cyclohexane shouldbe limited to 0.10 and/or the ratio of hydrogenatingactivity/isomerizing activity should be greater than 10.

[0007] The catalytic test that makes it possible to monitor the acidityof the catalysts is carried out according to the following operatingprocedure:

[0008] The catalysts are sulfurized in situ under dynamic conditions inthe tubular fixed-bed reactor that is traversed by a catatest-type pilotunit (manufacturer Vinci Technologies), whereby the fluids circulatefrom top to bottom. The hydrogenating and isomerizing activities aremeasured immediately after the pressurized sulfurization withoutreexposure to air with the hydrocarbon feedstock that was used tosulfurize the catalysts.

[0009] The sulfurization and test feedstock consists of 5.8% dimethyldisulfide (DMDS), 20% toluene and 74.2% cyclohexane by weight. Thestabilized catalytic activities of equal volumes of catalysts thus aremeasured in the hydrogenation reaction of the toluene. The follow-up tothe isomerization of the cyclohexane, diluting toluene, makes itpossible to estimate the acidity of the catalysts.

[0010] The conditions for measuring activity are as follows (taking intoconsideration total vaporization and the ideal gas law)

[0011] Total pressure: 6.0 MPa

[0012] Toluene pressure: 0.38 MPa

[0013] Cyclohexane pressure: 1.55 MPa

[0014] Hydrogen pressure: 3.64 MPa

[0015] H₂S pressure: 0.22 MPa

[0016] Catalyst volume: 40 cc

[0017] Feedstock flow rate: 80 cc/h

[0018] Hourly volumetric flow rate: 2 l/l/h⁻¹

[0019] Hydrogen flow rate: 36l/h

[0020] Sulfurization and test temperature: 350° C. (3° C./min)

[0021] Sampling of the liquid effluent is analyzed by gas phasechromatography. The determination of molar concentrations in unconvertedtoluene (T) and concentrations of hydrogenation products: methylcyclohexane (MCC6), ethyl cyclopentane (EtCC5) and dimethyl cyclopentane(DMCC5) make it possible to calculate a hydrogenation rate of tolueneX_(HYD) defined by:

X_(HYD)(%)=100*(MCC6+EtCC5+DMCC5)/(T+MCC6+EtCC5+DMCC5)

[0022] The cyclohexane isomerization rate X_(ISO) is calculated in thesame way from concentrations of unconverted cyclohexane and its reactionproduct, methyl cyclopentane. Whereby the hydrogenation reaction oftoluene and isomerization of the cyclohexane are on the order of 1 underour test conductions, and the reactor acts like an ideal piston reactor,hydrogenating activity A_(HYD) and isomerizing activity A_(ISO) of thecatalysts are calculated by applying the formula:

Ai=In(100/(100−X_(i))).

[0023] The ratio of hydrogenating activity to isomerizing activity H/Ais equal to A_(HYD)/A_(ISO).

[0024] The hydrodesulfurization processes of this invention can beapplied to, for example, petroleum fractions such as the crudepetroleums of degree, API that are less than 20, the extracts ofasphaltic sands and oil shales, atmospheric residues, vacuum residues,asphalts, deasphalted oils, deasphalted vacuum residues, deasphaltedcrudes, heavy fuels, atmospheric distillates and vacuum distillates orelse with hydrocarbons other than the carbon liquefiers.

[0025] The hydrorefining and hydroconversion reactions of thesehydrocarbon feedstocks (hydrotreatments) can be carried out in a reactorthat contains the catalyst that is arranged in a fixed bed. Anotherapplication of the invention is the use of these same catalysts in aneffervescent bed, particularly within the framework of hydrotreatments.

[0026] In the fixed-bed or effervescent-bed processes, thehydrotreatments that are intended to eliminate the impurities such assulfur, nitrogen, and metals and to lower the mean boiling point orthese hydrocarbons are usually used at a temperature of about 320 toabout 470° C., preferably about 350 to 450° C., under a partial hydrogenpressure of about 3 MPa (mega Pascal) to about 30 MPa, preferably 5 to20 MPa, at a volumetric flow rate of about 0.1 to about 6 volumes offeedstock per volume of catalyst and per hour, preferable 0.2 to 2volumes per volume of catalyst and per hour, whereby the ratio ofgaseous hydrogen to liquid hydrocarbon feedstock is between 100 and 5000normal cubic meters per cubic meter (Nm³/m³), preferably between 200 and1500 (Nm³/m³)

[0027] The catalysts of this invention generally have the followingcomposition:

[0028] at least one metal of group VIB: 5 and 40% by weight of oxide,preferably molybdenum or tungsten,

[0029] at least one metal of group VIII: 0.1 to 10% by weight of oxide,preferably iron, cobalt and nickel,

[0030] at least one porous oxide substrate such as aluminas orsilica-aluminas. It is preferred to use substrates that contain alumina:40 to 94.6% by weight of an oxide substrate relative to the total massof the catalyst,

[0031] optionally at least one dopant that is selected from the groupthat consists of phosphorus, boron, silicon and halogens; 0 to 10% byweight overall of P₂O₅, SiO₂ , B₂O₃, and/or halogens.

[0032] The catalysts according to the invention can be prepared by anysuitable methods, in particular by the methods that are described inFrench Patents No. 97/07149, 87/09 359, 96/15 622 or else 96/13 797. Asan example and without limiting the scope, the first catalyst, which canbe of NiCoMo type without a dopant, can be prepared by impregnation ofan alumina by an aqueous solution that contains a molybdenum precursor,a cobalt precursor and a nickel precursor. The second catalyst, whichcan be of NiMoP type, can be prepared, as an example, by co-impregnationof an alumina by an aqueous solution that contains a molybdenumprecursor, a nickel precursor and a phosphorus precursor.

[0033] The optional metals and dopants can be introduced at any momentof the preparation, in particular by impregnation on a substrate that isalready formed or introduced during the synthesis of the substrate.

[0034] The catalysts that are described in this invention are shaped inthe form of grains of different shapes and sizes. They are used ingeneral in the form of cylindrical extrudates or multilobar extrudates,such as bilobar, trilobar, or multilobar extrudates of straight ortwisted shape, but they can optionally be produced and used in the formof crushed powder, tablets, rings, balls, wheels. They have a specificsurface area that is measured by nitrogen adsorption according to theBET method (Brunauer, Emmett, Teller, Am. Chem. Soc., Vol. 60, 309-316(1938) between 50 and 600 m²/g, a pore volume that is measured bymercury porosimetry between 0.2 and 1.5 cm³/g and a distribution of poresize that can be monomodal, bimodal or polymodal.

[0035] The catalysts of this invention are preferably subjected to asulfurization treatment that makes it possible to transform, at least inpart, the metallic sulfide radicals before they are brought into contactwith the feedstock that is to be treated. This activation treatment bysulfurization is well known to one skilled in the art and can be carriedout for any method that is already described in the literature.

[0036] A standard sulfurization method that is well known to one skilledin the art consists in heating the mixture of solids under the flow of ahydrogen and hydrogen sulfide mixture or under the flow of a nitrogenand hydrogen sulfide mixture at a temperature of between 150 and 800°C., preferably between 250 and 600° C., generally in a flushed-bedreaction zone.

[0037] The applicant discovered, surprisingly enough, that the treatmentof a hydrocarbon feedstock of distillation residue type, previouslypartially demetallized, which circulates in at least one catalyst ofcontrolled acidity or successively in at least two catalysts ofincreasing acidity or a decreasing hydrogen/acidity ratio, providedbetter performance levels in hydrodesulfurization (HDS),hydrodenitrating (HDN) and hydrodecarbonation (HDCCR) with a weakerdeactivation and therefore a better service life than the use of asingle catalyst of uncontrolled acidity.

[0038] The examples below illustrate the invention described without,however, limiting its scope:

EXAMPLE 1 Preparation of the Alumina Substrate that is Part of theComposition of the Catalysts of the Invention

[0039] We manufactured a substrate based on alumina in a large quantityto be able to prepare the catalysts that are described below from thesame shaped substrate. To do this, we used a matrix that consists ofultrafine tabular boehmite or alumina gel that is marketed under thename SB3 by the Condéa Chemie GmbH Company. This gel was mixed with anaqueous solution that contains nitric acid at 66% (7% by weight of acidper gram of dry gel), then mixed for 15 minutes. At the end of thismixing, the paste that is obtained is passed through a die that hascylindrical orifices of a diameter that is equal to 1.3 mm. Theextrudates are then dried for one night at 120° C. and then calcined at550° C. for 2 hours under moist air that contains 75% by volume ofwater. Cylindrical extrudates are thus obtained that have a 1.2 mmdiameter, a specific surface area of 243 m²/g, a pore volume of 0.61cm³/g and a monomodal pore size distribution that is centered on 100 Å.The analysis of the matrix by x-ray diffraction proves that the latterconsists only of cubic gamma alumina of low crystallinity.

EXAMPLE 2 Preparation of Catalyst A (NiCoMo/Al₂O₃) According to theInvention

[0040] We impregnated in the dry state the extruded substrate of Example1 by an aqueous solution that contains molybdenum salts, cobalt saltsand nickel salts. The molybdenum salt is ammonium heptamolybdateMo₇O₂₄(NH₄)₆.4H₂O, the cobalt salt is cobalt nitrate Co(NO₃)₂.6H₂O, andthe nickel salt is nickel nitrate Ni(NO₃)₂ .6H₂O. After maturation atambient temperature in a water-saturated atmosphere, the impregnatedextrudates are dried for one night at 120 C. then calcined at 500° C.for 2 hours under dry air. The final content of molybdenum trioxide is14.5% by weight of the finished catalyst. The final content of cobaltoxide CoO is 2.4% by weight of the finished catalyst. The final contentof nickel oxide NiO is 0.8% by weight of catalyst. Catalyst A that isthus obtained is representative of a catalyst according to thisinvention (see Example 6).

EXAMPLE 3 Preparation of catalyst B (NiMoP/alumina) According to theInvention

[0041] We impregnated in the dry state the extruded substrate of Example1 by an aqueous solution that contains ammonium heptamolybdateMo₇O₂₄(NH₄)₆.4H₂O and nickel nitrate Ni(NO₃)₂.6H₂O to which phosphoricacid H₃PO₄ was added. The same stages of maturation, drying andcalcination as for the preparation of catalyst A of Example 2 were used.The final content of molybdenum trioxide is 16.0% by weight of thefinished catalyst. The final content of nickel oxide is 4.0% by weightof the finished catalyst. The final content of phosphorus, expressed inpentaoxide, is 6% by weight of the finished catalyst. Catalyst B that isthus obtained is representative of a catalyst according to thisinvention (see Example 6).

EXAMPLE 4 Preparation of a Catalyst C (NiMoSi/alumina) According to theInvention

[0042] We impregnated in the dry state the extruded substrate of Example1 by an aqueous solution that contains ammonium heptamolybdateMo₇O₂₄(NH₄)₆.4H₂O and nickel nitrate (Ni(NO₃)₂.6H₂O. The stages ofmaturation, drying and calcination, as for the preparation of catalyst Aof Example 2, were used. This precursor NiMo that was thus obtained wasagain impregnated, but this time by an aqueous solution that containsthe Rhodorsil silicone emulsion EP1. The final content of molybdenumtrioxide is 14.0% by weight of the finished catalyst. The final contentof nickel oxide is 3.4% by weight of the finished catalyst. The finalcontent of silicon, expressed in SiO₂, is 1.8% of the weight of thefinished catalyst. Catalyst C that is thus obtained is representative ofa catalyst according to this invention (see Example 6).

EXAMPLE 5 Preparation of a Catalyst D (NiMoPSi/alumina) not According tothe Invention

[0043] We impregnated in the dry state the extruded substrate of Example1 by an aqueous solution that contains ammonium heptamolybdateMo₇O₂₄(NH₄)₆.4H₂O and nickel nitrate Ni(NO₃)₂.6H₂O to which phosphoricacid H₃PO₄ is added. The same stages of maturation, drying andcalcination as for the preparation of catalyst A of Example 2 were used.This precursor NiMoP that was thus obtained was again impregnated, butthis time by an aqueous solution that contains the Rhodorsil siliconeemulsion EP1. The final content of molybdenum trioxide is 16.0% byweight of the finished catalyst. The final content of nickel oxide is 4%by weight of the finished catalyst. The final content in phosphorus,expressed in pentaoxide, is 6% by weight of the finished catalyst. Thefinal content of silicon, expressed in SiO₂, is 4% by weight of thefinished catalyst. Catalyst D that was thus obtained is not inaccordance with the invention (see Example 6).

EXAMPLE 6 Hydrogenation and Acidity Tests on Model MoleculesHydrogenation of Toluene, Isomerization of Cyclohexane:

[0044] Catalysts A to D, described above, are sulfurized in situ underdynamic conditions in the tubular fixed-bed reactor that is traversed bya catatest-type pilot unit (manufacturer Vinci Technologies), wherebythe fluids circulate from top to bottom. The measurements ofhydrogenating and isomerizing activity are made immediately after thepressurized sulfurization without reexposure to air with the hydrocarbonfeedstock that was used to sulfurize the catalysts.

[0045] The sulfurization and test feedstock consists of 5.8% by weightor dimethyl disulfide (DMDS), 20% by weight of toluene and 74.2% byweight of cyclohexane. The stabilized catalytic activities or equalvolumes of catalysts A to D thus are measured in the hydrogenationreaction of toluene. The follow-up of the isomerization of thecyclohexane, which dilutes toluene, makes it possible to estimate theacidity of the catalysts.

[0046] The conditions for activity measurement (based on a totalvaporization and the ideal gas law) are as follows:

[0047] Total pressure: 6.0 MPa

[0048] Toluene pressure: 0.38 MPa

[0049] Cyclohexane pressure: 1.55 MPa

[0050] Hydrogen pressure: 3.64 MPa

[0051] H₂S pressure: 0.22 MPa

[0052] Catalyst volume: 40 cc

[0053] Feedstock flow rate: 80 cc/h

[0054] Hourly volumetric flow rate: 2 l/l/h⁻¹

[0055] Hydrogen flow rate: 36 l/h

[0056] Sulfurization and test temperature: 350° C. (3° C./min).

[0057] Samplings of the liquid effluent are analyzed by gas phasechromatography. The determination of molar concentrations in unconvertedtoluene (T) and concentrations of the hydrogenation products: methylcyclohexane (MCC6), ethyl cyclopentane (EtCC5) and dimethyl cyclopentane(DMCC5) make it possible to calculate a toluene hydrogenation rateX_(HYD) that is defined by:

X_(HYD)(%)=100*(MCC6+EtCC5+DMCC5)/(T+MCC6+EtCC5+DMCC5)

[0058] The isomerization rate of cyclohexane X_(ISO) is calculated inthe same way from concentrations of unconverted cyclohexane and itsreaction product, methyl cyclopentane.

[0059] Whereby the hydrogenation reaction of toluene and isomerizationof the cyclohexane were of the first order under our test conditions,and the reactor acts as an ideal piston reactor, hydrogenating activityA_(HYD) and isomerizing activity A_(ISO) of the catalysts are calculatedby applying the formula:

Ai=In(100/(100−X_(i))).

[0060] Table 1 compares the hydrogenating and isomerizing activities ofdifferent catalysts, as well as the H/A ratio that is defined by theA_(HYD)/A_(ISO) ratio between the hydrogenating activity and theisomerizing activity. TABLE 1 Hydrogenating and Isomerizing Activitiesof Catalysts A to D Catalyst Formula A_(HYD) A_(ISO) A_(HYD)/A_(ISO) ANiCoMo/alumina 0.50 0.005 100 B NiMoP/alumina 0.65 0.009 72 CNiMoSi/alumina 0.78 0.011 71 D NiMoPSi/alumina 0.60 0.078 7

[0061] Table 1 shows that catalysts A to C are in accordance with thefirst aspect of the invention, since the isomerization activity is,under these measuring conditions, less than 0.10, and that the ratiobetween the hydrogenating activity and the isomerizing activity,A_(HYD)/A_(ISO), is greater than 10. On the contrary, catalyst D is notin accordance with the invention, since the ratio between thehydrogenating activity and the isomerizing activity is less than 10.

EXAMPLE 7 Pilot Tests Evaluating the HDT Performance of PetroleumDistillation Residues of Catalysts A to D

[0062] Catalysts A and D have been evaluated in themselves orconcatenated in a hydrotreatment pilot test of a vacuum distillationresidue of Light Arabian origin, previously partially demetallized. Thisfeedstock was previously demetallized in a fixed-bed pilot unit by ahydrotreatment catalyst, such as the one that is described in, forexample, French Patent No. 97/07149.

[0063] The main characteristics of this demetallized residue are postedin Table 2 below: TABLE 2 Characteristics of previously partiallydemetallized vacuum residues Demetallized vacuum residue Density 15/40.989 Sulfur (% by weight) 2.3 Ni (ppm by weight) 12 V (ppm by weight)18 Asphaltenes C7 (% by weight) 3.9 Cnradson carbon (% by weight) 14 N(ppm by weight) 3600

[0064] This feedstock is treated on a hydrotreatment pilot unit ofpetroleum residues comprising two tubular fixed-bed reactors arranged inseries. Each reactor can be filled with 1 liter of catalyst. The flow offluids (petroleum+hydrogen residues) is upward in the reactor.

[0065] When each catalyst is evaluated by itself, only the first reactoris loaded with a liter of catalyst. When it is desired to evaluate theconcatenation of catalysts, the first catalyst is loaded into the firstreactor and the second into the second reactor. In all cases, the flowrates of residues and of hydrogen gas are adjusted to keep constant thehourly volumetric flow rate of the residue and the ratio between the gasflow rate and the liquid flow rate (Table 3).

[0066] After a sulfurization stage by circulation in the reactors of avacuum distillate fraction that contains 2% by weight of sulfur at afinal temperature of 350° C., the unit is operated with the partiallydemetallized vacuum residue that is described above. The operatingconditions that are used at the beginning of the test are as follows:TABLE 3 Operating Conditions of Pilot Tests Total pressure 150 MPaTemperature at the beginning of 370° C. the cycle Hourly volumetric flowrate of 0.3 h⁻¹ the residue Hydrogen recycling 1000 hours at 1 H₂/l offeedstock

[0067] After 500 hours of stabilization under these conditions, theperformance levels of hydrodesulfurization (HDS) hydrodemetallization(HDM), Conradson carbon reduction (HDCCR) and hydrodenitration (HDN) aremeasured and calculated in the following way:

[0068] HDS (% by weight)=((% by weight of S)feedstock−(% by weight ofS)formula/% by weight of S feedstock*100

[0069] HDM (% by weight)=((ppm by weight of Ni+V)feedstock−(ppm byweight of Ni+V)formula)/ppm by weight of Ni+V feedstock*100

[0070] HDCCR (% by weight)=((% by weight of CCR)feedstock−(% by weightof CCR)formula)/% by weight of CCR feedstock*100

[0071] HDN (% by weight)=(ppm by weight of N)feedstock−(ppm by weight ofN)formula)/ppm by weight of N feedstock*100

[0072] The performance levels that are obtained at the end of 500 hoursin the catalysts are as follows (Table 4): TABLE 4 Performance Levels atthe End of 500 Hours at 370° C. HDS HDM HDCCR HDN (% by (% by (% by (%by Catalytic System weight) weight) weight) weight) Catalyst A 75.1 5138 38.3 Catalyst B 74.5 49.3 38.5 39 Catalyst C 78.0 53.1 39.5 39.2Catalyst D 73.5 51 35.5 38.5 Catalyst A + B 75.0 50.2 38.9 38.6 CatalystA + C 76.5 52.1 39.0 38.2 Catalyst C + A 75.5 51.8 38.5 39.0

[0073] After this period of 500 hours, the tests are conducted by aimingat keeping a constant HDS rate of 78% by weight throughout the cycle.The purpose of this is to evaluate the relative stability of thedifferent catalysts or combination of catalysts. For this purpose, thedeactivation of the catalyst in HDS is compensated by a gradual increaseof the reaction temperature.

[0074] After a total operating time of 2500 hours, the temperatures ofthe reactors and the performance levels that are obtained are as follows(Table 5): TABLE 5 Performance Levels at the End of 2500 Hours HDS HDM(% HDCCR HDN Catalytic Temperature (% by by (% by (% by system (° C.)weight) weight) weight) weight) Catalyst A 392 78 55.1 40.5 39.2Catalyst B 394 78 52.5 41.9 40.1 Catalyst C 390 78 55.6 42.8 40.1Catalyst D 400 78 53.1 36.5 37.2 Catalyst A + B 389 78 53.9 45.1 42.1Catalyst A + C 386 78 53.8 45.0 41.5 Catalyst C + A 391 78 55.3 41.539.9

[0075] It appears that catalysts A, B or C that meet the criteria ofacidity defined in this patent are initially more active in refining,primarily HDS; this is not the case of catalyst D whosehydrogenation/acidity balance does not meet the criteria of theinvention. This advantage is also observed with still more significantdeviations, after 2500 hours of operation, reflecting a greaterstability over time of the catalysts that meet this criterion.

[0076] The advantage (second aspect of the invention) of circulating thefeedstock in at least two catalysts of growing acidity (increasing Aand/or decreasing H/A) is primarily visible at the stability level it isobserved that the A+B or A+C combinations are more high-performing-after2500 hours of operation than the catalysts that are used by themselves,and considerably more high-performing than a single catalyst, used byitself and not meeting the criteria of the invention. These observationshave been made with regard to both HDS and to the HDCCR and HDN rates.This leads to a better potential of hydrotreated product as a feedstockof a catalytic cracking unit.

[0077] Putting the most acid catalyst first (case C+A) leads to a lowerinitial performance level and a lower stability of this performancelevel relative to those of the system that puts the, least acid catalystfirst (case A+C) as is described in the invention.

[0078] On the contrary, in the case where the feedstock is circulated ona catalyst that has a high acidity or a low hydrogenation/aciditybalance (catalyst D), it appears necessary to very strongly increase thetemperature (400° C.) to keep an HDS rate of 78%. This type of catalystthus leads to neither a high performance level at the beginning of thecycle nor stability that is compatible with a satisfactory cycle length.

[0079] The preceding examples can be repeated with similar success bysubstituting the generically or specifically described reactants and/oroperating conditions of this invention for those used in the precedingexamples. Also, the preceding specific embodiments are to be construedas merely illustrative, and not limitative of the remainder of thedisclosure in any way whatsoever.

[0080] The entire disclosure of all applications, patents andpublications, cited above and below, and of corresponding Frenchapplication number 00/02.284 filed Feb. 23, 2000 and U.S. ProvisionalApplication 60/186,300 filed Mar. 1, 2000, are hereby incorporated byreference in their entirety.

[0081] From the foregoing description, one skilled in the art can easilyascertain the essential characteristics of this invention, and can makevarious changes and modifications of the invention to adapt it tovarious usages and conditions.

[0082] Also, the term “effervescent” can be replaced by “bubbling” whichmay be a more common term in connection with catalytic beds.

1. Process for conversion of hydrocarbons in the presence of at leastone catalyst of controlled acidity, characterized in that the level ofactivity of said catalyst in isomerization is less than 0.10 and in thatthe ratio of hydrogenating activity to isomerizing activity is greaterthan
 10. 2. Process according to claim 1 applied to the hydrotreatmentsof a hydrocarbon feedstock.
 3. Process according to claim 2, wherein thefeedstock circulates successively in at least two catalytic beds ofcatalysts defined in claim 1, also wherein the first catalyst is: theone that contains cobalt if the others do not contain it, or the onethat has lower acidity and/or the ratio of hydrogenating activity toisomerizing activity is higher in the case where all the catalystscontain cobalt or in the case where no catalyst contains cobalt. 4.Process according to one of claims 1 to 3 that is carried out in atleast one fixed-bed reactor.
 5. Process according to one of claims 1 to3 that is carried out in at least one effervescent-bed reactor.